Though not an explicit enemy of Okonkwo in the traditional sense, Unoka does indeed antagonize his son. The memory of Unoka’s debt and shame haunts Okonkwo throughout the novel. Unoka’s actions basically set the template for everything Okonkwo will oppose – frivolity (in Unoka’s love of music), laziness, dislike of blood and violence, dependence on charity. It’s largely Unoka’s actions that shape Okonkwo into the man he becomes. Thus, it would be interesting to imagine what type of man Okonkwo would have become if Unoka had been a respectable member of society.
The missionaries and the white government that they bring act as a general enemy for the whole of the Igbo people. They invade the Igbo people’s land and treacherously destroy Umuofia from the inside out. They use the Igbo people’s superstitions against them, claiming the superiority of their own god when the expected wrath of the native gods does not come to fruition. In this manner, they persuade and slowly win more and more converts to their side. They divide and conquer, compromising the Umuofia’s sense of unity, rendering the clan unable to set up any uniform kind of resistance.
For Okonkwo personally, the worst aspect of the missionaries is his perception of the effeminate characteristics they impose on the people of Umuofia. Because the Umuofia can no longer act as a single unit to oppose the white man, he considers his people indecisive, passive, and weak rather than the proud warriors they once were. Not only does Okonkwo despise the white men for bringing weakness to the clan, he is also specifically enraged by the government they impose on the Umuofia. Okonkwo in particular suffered a humiliating and unjust beating by the white court, and offense which he cannot forgive.